Human beings are capable of recognizing the source location, i.e., distance and orientation, of sounds heard through the ears through a variety of auditory cues related to head and ear geometry, as well as the way sounds are processed in the brain. Surround sound systems attempt to enrich the audio experience for listeners by outputting sounds from various locations which surround the listener.
Typical surround sound systems utilize an audio signal having multiple discrete channels that are routed to a plurality of speakers, which may be arranged in a variety of known formats. For example, 5.1 surround sound utilizes five full range channels and one low frequency effects (LFE) channel (indicated by the numerals before and after the decimal point, respectively). For 5.1 surround sound, the five full range channels would then typically be arranged in a room with three of the full range channels arranged in front of the listener (in left, center, and right positions) and with the remaining two full range channels arranged behind the listener (in left and right positions). The LFE channel is typically output to one or more subwoofers (or sometimes routed to one or more of the other loudspeakers capable of handling the low frequency signal instead of dedicated subwoofers). A variety of other surround sound formats exists, such as 6.1, 7.1, 10.2, and the like, all of which generally rely on the output of multiple discrete audio channels to a plurality of speakers arranged in a spread out configuration. The multiple discrete audio channels may be coded into the source signal with one-to-one mapping to output channels (e.g. speakers), or the channels may be extract from a source signal having fewer channels, such as a stereo signal with two discrete channels, using other techniques like matrix decoding to extract the channels of the signal for playout.
Surround sound systems have become popular over the years in movie theaters, home theaters, and other system setups, as many movies, television shows, video games, music, and other forms of entertainment take advantage of the sound field created by a surround sound system to provide an enhanced audio experience for listeners. However, there are several drawbacks with traditional surround sound systems, particularly in home theater applications. For example, creating an ideal surround sound field is typically dependent on optimizing the physical setup of the speakers of the surround sound system, but sometimes the speakers may not be set up or arranged as desired due to physical constraints and other limitations. Thus, there is a need to simulate an optimal surround sound field to provide high quality audio experience even under the circumstances where the speakers cannot or are not arranged or installed as required. In other words, it is desirable to recreate a perception in the listener that the sounds are localized as if they are originated from desired locations which may be independent from the location of the speakers.
It has been proposed that the source location of a sound can be simulated by manipulating the source signal to sound as if it originated from a desired location, a technique often referred to in audio signal processing as “sound localization.” Many known audio signal processing techniques attempt to recreate sound fields which simulate spatial characteristics of a source audio signal using what is known as a Head Related Impulse Response (HRIR) function or Head Related Transfer Function (HRTF). A HRTF is generally a Fourier transform of its corresponding time domain head-related impulse response (HRIR).
It is within this context that aspects of the present disclosure arise.